This Instructable covers how I made a Smoker (for smoking meats) from an old office filing cabinet. The end result is a smoker that has a drawer for the fire, and a couple drawers for meat. Its a direct smoker, much like the black cylindrical metal ones you can get fairly cheap at the local hardware store, so regulating smoke and temperature takes a little practice.

Step 1: Stuff You Need

Materials

Metal filing cabinet. I got mine free from work as it was old and the cloth cushion top was torn. Mine is also an under-desk sized one, though this should work for the full-height ones as well (Tower of smokin meat!).
3/4" Oak Veneered plywood 2'x2' (Might need larger if your cabinet is longer/deeper. Mine was 2'x1'-5")
~8' of solid oak edge moulding. I used a fairly simple astragal pattern, 1.25" (half-round top with a chamfered curve extending the bottom).
Grill grates. They make grill grates that can be extended to fit any grill. If you can't find one to the exact size you need, get these instead.
Washers, grommets, screws, nuts. Various small bits of hardware
Finishing nails
Aircraft remover: Highly effective at removing everything down to bare metal. BE CAREFUL WITH IT, it will burn the #@$! out of you if you get so much as a drop on your skin, and removes/eats paints and plastics and just about anything not metal.
Grill/high-temp paint (Rustoleum flat black grill paint)
Shelf support pegs (metal)
Wood glue
Wood stain
Polyurethane

Tools

Drill and bits
Tin snips
Hammer
Pliers
screw driver
Thick leather gloves (tin snips leave super sharp serrated edges!)
Rubber gloves (made of stuff Aircraft remover will not eat, ie: not nitrile. Thick yellow kitchen gloves seem to work, or heavy duty PVC ones)
paint scraper (I got away with a cheap plastic set, went through 3 of them though as aircraft remover slowly softened them up into mush)
Miter saw
Grommet punch/press (should come with any grommet kit)
hack saw or dremmel cuttoff wheel (bolt cutters will do too)
wood clamp
Vice (helpful, not necessary)

Step 2: Take the Cabinet Apart

Remove the drawers from the cabinet. There should be a button or latch of some kind on the side of the drawer to release it from the rails.
Remove the rails from the cabinet. They usually hook into place, so lifting them at either end should free them. Look to see if there is a screw also holding them in place.
Remove the rails from the sides of the drawers. These could be screwed in or might have tabs that slide and latch in place.
Remove the top. Mine was held in place with 4 large screws from underneath.
Remove any handle from front of the drawers. Some cabinets have metal insert handles (mine did), some have external handles, some have handled formed in the bent face of the drawer such that there isn't really anything to remove.
Remove the lock mechanism. This is comprised of a metal beam that runs vertically along the back of the cabinet and is raised and lowered by a metal arm and the key lock. (not necessary, you could potentially have a locking smoker ;) )

Step 3: Remove and Replace Plastic Bits

SInce the inside will be getting quite hot, its not a good place for plastic or rubber or really anything not metal to be. Find all the plastic bits and remove them, but make note of what they do as you might have to replace them with metal parts.

For mine, there were a few rubber drawer bumpers, plastic slide bushings and most critically the rollers on the large drawer's sliding frame were all plastic. I replaced the rollers with washers, machine screws and nuts and flattened out brass grommets of proper size.

Step 4: Strip It Bare

Using Aircraft Remover (VERY CAREFULLY, with good gloves, safety glasses, long sleeved shirt and full length pants and close toed shoes and probably a hat (scraping might fling it in all sorts of directions!), and in a well ventilated space with newspaper or something to catch the drippings and paint flakes) strip all the paint off the cabinet and drawers. To use Aircraft Remover, follow the directions on the can you have. Typically you use a brush or scraper to spread it around on the painted surface and let it sit. It will start to bubble and the paint will start to crinkle and peel off the metal. After a few minutes when it looks good and ready, use the scraper to scrape the goop off. Be sure to have more newspaper or something to wipe it off the scraper and contain it for disposal. Repeat as needed on the cracks and spots that might be left. Be prepared to dispose of anything it comes in contact with (gloves, scraper, clothing, skin, etc), this stuff is nasty. Once done, wash it down with soap and water and rinse it off.

Step 5: Paint!

Using high-temp paint (I used flat-black Grill specific Rustoleum), give the cabinet and drawers a few good coats of paint. I went through a few spray cans to get a good coating. This is important not only for making it look nice, but also sealing the metal and retarding the rust that will happen. You will likely want to sand and repaint parts of it, especially the parts near the fire drawer, each year or two. The heat accelerates the rusting, and the lower parts tend to get wet more frequently from standing water, morning dew, and accidental garden hose.

Step 6: Setup the Meat Drawers

For this to be a functioning smoker, the drawers need to allow smoke and heat through them to cook the meat. At this point you should determine how you want the drawer layout to be. My filing cabinet had places for the sliders to go to re-arrange the drawers about any way I wanted, so I set it up with the large drawer in the middle. This let me use a small drawer for the fire box on bottom, and have another small drawer at the top for more meat.

Cut the center out of the drawers that will be used for meat using tin snips, leaving about 1" around the edges for the Grill to rest on and a tab or two to allow for bolting it together. Adjust and/or cut the grill to fit and secure it using washers and screws and nuts, the washers sandwiching the grill between some rungs and the flange left around the bottom of the drawer.

For the big drawer, I added an upper shelf. I used two strips of plywood scrap left over from cutting the lid to size, and fit them in the groove in the side of the drawer used to guide the hanging folders and divider. These cross-members can slide around a bit, so I added a couple screws to each one with the heads sticking up 1/4" or so, so I could fit another grill piece on top with the screws sticking up between the rungs to keep them in place. I also added rib racks to the upper drawer to allow hanging thin strips of meat. All together this setup can process about 3lbs of beef into jerky per session.

Leave the fire drawer alone for now.

Step 7: Setup the Fire Drawer

The fire drawer works a bit differently. In order for the fire to be sustained, it needs to get air. In order to get smoke, this fire needs to be slightly suffocated to burn inefficiently, and consequently this helps to control the temperature. To make this adjustable, I used the metal divider in the large drawer as a damper, laying it flat on the bottom of the drawer and sliding it back and forth to cover/uncover a grid of holes drilled through the bottom. This works somewhat well at controlling the draft. Air still leaks into the cabinet through gaps between the drawer fronts and frame, and up through the bottom around the drawer sides, but this helps significantly.

Using a straightedge, draw a grid with ~1" spacing on the bottom of the drawer. Lay the divider flat on the drawer bottom and setup an armature or something to allow sliding it (I made use of the metal handle and lock bars also present on the divider, and a couple rivets to hold things together). Mark the width of the divider on the bottom where you want it to be closed, then slide it to the open position and mark again. Drill a 1/4" or so hole at several of the intersections (I did about 20) in the area covered when in the closed position. Drill a few holes in the section that is not covered, just to make sure the fire gets some air (think of it as the "idle" on a throttle).

*Note that with holes drilled in this drawer, ash and potentially small bits of burning coals (and lighter fluid!) will fall through to the ground, since most cabinets are open on the bottom. You should put down sand or a catch pan of some kind under the smoker when using it if this worries you.

Next setup the fire grate. This needs to sit off the bottom we just drilled, allowing room for the damper to slide back and forth and allow an air draft below the coals. To hold the grate up, I used a few shelf support pegs

Step 8: Put It Back Together

Re-attach the side rails to the drawer. Re-install the rails to the cabinet in the way you want the drawer layout to be. Reinstall the drawers to the cabinet.

Step 9: Building the Lid

The top of the cabinet I had was a cloth and foam covered thing that was falling apart. It was designed to be a seat I think, useful for when someone stops by your desk to work on something and needs a place to sit for a few minutes. Anyway, it had to go. To make things look nice, I got a good veneered plywood and some molding to make a nice stained oak top.

I cut the plywood to the dimensions of the top of the cabinet, then cut the moulding to the outer dimensions of the plywood top with a compound miter saw (just 45 degree angles with the flat side against the guard, nothing too compound about this job). Using wood glue and finish nails I glued and tacked the moulding into place, flush with the top of the plywood, leaving a bit of an overhang underneath. I made a quick clamp from the metal locking bar I pulled out of the cabinet and para-cord to hold the junction tight together. The overhanging moulding works well as it keeps the lid in place. Once the glue dried I went back over the whole thing with sand paper to smooth out any rough spots and level the seams and round the corners, then went around again with wood filler, filling in any gaps still visible and sanded it all smooth again when that cured.

Using wood stain and a rag to apply it, I stained the lid, then coated it in multiple coats of an outdoor rated polyurethane finish. I left the underside unstained and unfinished, as I didn't want any chance of either stain or polyurethane to contaminate the meats below. For extra longevity, you could tack a sheet of metal to the underside (be wary of anything galvanized), but I have found it doesn't really get hot enough to severely damage it, past charring just a bit. I foresee this lid lasting quite a few more years before I need to think about replacing it. The bottom of the cabinet and fire drawer will probably rust out first.

Step 10: New Handles

The handles on the cabinet I got were metal coated in some foamy rubberized paint of some kind, and inset to the face of the drawer. I removed them by removing the two screws on the inside of the drawer that held them in place, then fabricated new inserts from scraps of the plywood from the lid (which happened to be the perfect thickness).

Cut strips of the wood to the exact dimensions of the opening left from removing the handles, maybe slightly larger so you can sand and file it into a perfect fit. You want as little a gap as possible for best appearances here. Test fit and file and sand and test fit again until perfection is acquired! For the pulls, I used leftover moulding from the lid, and a piece from the tailings bin (I had only enough original moulding left over for just two pulls) at the local hardware store I got for cheap that had an undercut to it. Using a compound miter saw, I cut 6" segments with tapered ends. I then made an undercut using a drill and dremmel, and drilled out a section of the wood strip where the under cut of the pull would go. I cut until I could easily get my fingers into the pull when it was sitting in place on the strip. Using a couple screws and wood glue, I secured the pulls to the wood strip inserts. I then stained the new handles using the same stain, and coated with the polyurethane. Once it was all cured, I attached the new handles to the drawers with screws through the original screw holes in the drawers.

Step 11: Time to Smoke!

With the drawer pulls and lid in place, its about ready for use! I did a couple dry-runs first to get a good smokey coating to the inside of the cabinet and make sure nothing plastic was hidden inside that might melt/burn/contaminate my cooking, as well as figure out how things would work. I lowered the cabinet so the bottom sat almost on the ground (it had screw-feet next to where the wheels were). This was to further restrict the amount of air the cabinet could draft in.

To operate, open the fire-drawer, load your coals and light them with minimal lighter fluid (or get them going outside the cabinet and move them in already glowing). Adjust the damper to the full-open position. Have your wood chips loaded and ready in a chip box (or chunks soaked and ready to add to the coals, whatever your preference). Once the flames die down from the initial start, close the drawer most of the way and open the top drawer just a crack to let a nice draft flow through, heating the cabinet to operational temperature while getting the coals going. Once the coals are ready, open the fire drawer again and close the damper most of the way (the exact setting takes practice to get right), add your wood chips/chunks, maybe some more coals to keep the heat going longer and close it up. Open the meat drawers and add your meat. Once loaded, simply slide the drawers closed and watch the smoke leak out through the cracks as it makes your meat nice and tasty! I suggest keeping a close eye on the meat the first few times you use it to figure out how it runs, maybe install a thermometer to keep track. You can also put in a water pan on the bottom drawer to keep things cool and add a bit of humidity to prevent things drying out too much.

After cooking, simply slide the fire drawer out completely, take it to your ash dump, and turn it over. All the spent coal ash and other remnants should fall out. Remove the fire grate and shake it out good, use a brush to get out as much as you can to prevent rusting (ash and heat will make it rust much faster than normal). Put the grate back in and slide the drawer back into place. Thats it! You now have a filing cabinet smoker!